1. Field of the Invention:
The present invention relates to a method for illuminance measurement of a vehicle lamp such as automotive headlamp.
2. Prior-art Statement
During periodic servicing and inspection of automobiles or in the inspection line following the assembling thereof, the main optical axis of the headlamp is checked to see that the headlamp is correctly fixed. For this purpose, a variety of headlamp testers have been developed.
Generally, conventional headlamp testers of such type use a photosensor such as photocell, etc. However, as more and more types of cars have been produced, the headlamp has also been diversified in type correspondingly and thus it is required to inspect each type of headlamp with high precision.
To this end, a headlamp tester has been proposed which is designed to pick up, by a TV camera, a luminous intensity distribution pattern of a light projected from a headlamp onto a screen, for example, and process the picked-up luminous intensity distribution pattern to check whether the main optical axis of the headlamp is correctly held. With this headlamp tester, it is possible to check the main optical axis with an improved precision and quickly adjust it.
In addition to the main optical axis check as mentioned above, however, the headlamp must be subject to a luminous intensity check. This luminous intensity check is separately done using a dedicated apparatus. Consequently, the luminous intensity check adds to the labor required for the headlamp inspection and requires additional time.
Also, for the above-mentioned headlamp tester, it has been proposed that the image information from the imaging means such as TV camera or the like should be utilized to measure the luminous intensity as well. However, since the TV camera uses an automatically collimated lens, it is not possible to precisely measure the true illuminance on the screen and thus the luminous intensity of the headlamp cannot be calculated.